Modern color negative films usually contain dyes coated in one or more layers for a variety of purposes. In addition to being utilized for spectral sensitization, dyes may be used for filtering specific wavelengths of exposing light (either as intergrain absorbers or in separate layers containing no silver halide), for antihalation and to adjust the background density (Dmin) of color negative films for printing purposes. Such preformed coated dyes (that is, dyes which are present in the element prior to exposure and development) are often referred to as "dummy dyes" to distinguish them from dyes that may be formed photographically (typically from coupler compounds) as a result of exposure and chromogenic development.
In the development of color photographic elements, bleach solutions are used to oxidize developed silver to silver ions for subsequent removal in fix solution by formation of soluble silver complexes. The bleach and fix solutions are sometimes combined into a single "blix" solution. Bleach solutions commonly contain complexes of ferric ion, such as ferric ethylenediaminetetraacetic acid (EDTA), as oxidizing agents. Prolonged use of such solutions for processing of photographic film can result in accumulation of substantial quantities of the corresponding ferrous ion complexes (such as ferrous EDTA), which can function as reducing agents. These reducing agents can cause reductive discoloration of dummy dyes (so called leuco dye formation). The formation of leuco dye in such seasoned bleaches is undesirable, not only because the resulting Dmin density provided by the dummy dye will be less than the optimum required for proper printing characteristics, but also because variabilities in Dmin can occur as seasoning of a bleach progresses.
Many cyan dummy dyes that have been used in color negative films for antihalation and for Dmin adjustment have suffered from a number of deficiencies, including loss of color in seasoned photographic bleach solutions or in bleaches of low oxidizing strength. Additionally, they may also have improper hue or suffer from changes in hue and/or density upon storage at low or high temperatures. For example, the dye of structure C1 has been used extensively in a number of commercial color negative films. The hue of this dye is suitable for Dmin adjustment and for antihalation purposes. However, dye C1 can undergo reductive discoloration when films containing it are processed in seasoned photographic bleaches or in bleaches of weak oxidizing power. ##STR2##
The dye of structure C2 dissolved in the high-boiling solvent N,N-diethyldodecanamide has also been used as a dummy dye in commercial color negative film. However, as illustrated in Examples below, this composition yields a dye hue that is too hypsochromic, and the extinction coefficient of dye C2 is also undesirably low. Due to the hypsochromic (shorter wavelength) absorption of a film containing dye C2 as a dummy dye in N,N-diethyldodecanamide relative to films containing dye C1, the printing characteristics of the two types of film can be sufficiently different to yield objectionable color balance differences when the two types of film are printed together using automatic high- speed printers. The N,N-diethyldodecanamide was used previously to facilitate dissolution of dye C2. U.S. Pat. No. 5,108,883 discloses the use of dye C2 dissolved in dibutyl phtahalate. While the hue of such a composition would be less hypsochromic and more suitable for proper printing, this composition also results in a low dye extinction coefficient and thus requires that more dye be coated to achieve the desired red density. ##STR3##
Thus, there has been a need to find replacements for such dummy dyes, particularly cyan dummy dyes, which replacements would exhibit high extinction coefficients to provide good cyan density with less dye, and low tendency to undergo leuco dye formation in seasoned bleaches or weak bleaches while retaining the desired spectral properties of dummy dyes such as dye C-1.